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Calibration

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6.2 VR Assignments

There are five variable resistors (VR) on the ACL-8111 board to allow

you making accurate adjustment on A/D and D/A channels. The function

of each VR is specified below:

VR No. Function

VR1 D/A full scale adjustment

VR2 D/A zero offset adjustment

VR3 A/D offset adjustment

VR4 A/D full scale adjustment

VR5 A/D programmable amplifier offset adjustment

6.3 D/A Calibration

The D/A input reference voltage should be connected to for calibration. You

may use the JP1 to select the -5V or -10V reference. The zero offset and full

scale of D/A channel can be turned through VR1 and VR2. The full-scale

gain of D/A is adjusted by VR1, and zero offsets are adjusted by VR2.

Note

: A precision voltmeter to measure the D/A output is very important.

The procedures of calibration are as follows:

Full scale adjustment :

1. Set JP1 to select -5V as reference voltage.

2. Connect VDM (+) to CN1 pin 30 and VDM (-) to A.GND.

3. Write digital data '4095' (0x0FFF) into D/A's digital data Register

(BASE+4 and BASE+ 5).

4. Adjust

VR1

until your voltmeter's voltage reading is equal to +5V

(reference voltage with opposite sign).

Offset zero adjustment:

1. Write digital data ' 0' (0x0000) to D/A's digital data register (BASE+4 and

BASE+ 5).

2. Adjust

VR2

until the your voltmeter's voltage reading is 0V.

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